Long-wall mining machines of the aforedescribed type generally have at least one of the deflection stations formed as a drive station and a device for determining and evaluating functional parameters of the endless working chain. The latter device can comprise sensors which may be inductive proximity sensors spaced apart and thus arranged to respond to the chain or passage of the flights or mining tools to generate corresponding measurement pulses.
With such mining machines, the device which monitors the functional parameters of the working chain has grown in significance in recent years because it allows the chain tension, the forces upon the chain and the stresses applied upstream and downstream of the working locations to be detected and potential chain breakage to be predicted. The device can serve to alert the operator to the danger of chain breakage or, in the case of automatic machine operations, can shut down the operation in the case of breakage of the development of an incipient condition which can lead to chain breakage.
In one monitoring system as described in Gluckauf 127 (1991), No. 17, 18 page 778 to 785, and 128 (1992), No. 3, page 189 to 193), the forces are detected directly as such and the chain sag is determined as a geometrical value. This is not consistent with integration of the technique into modern electronic monitoring and control systems.
In the long-wall mining machine of DE 35 24 338, two sensors are provided at such distances from one another that an increase in the link pitch of the chain can be detected or signaled.
DE 42 36 519 provides overload control of chain drives utilizing the pulses from sensors which detect the speed with which the drive motor operates the chain in a contactless manner and thus enables determination of an actual torque which can be compared to a setpoint torque to allow overload detection.